Functional Stimulation; Thermal Influences. 41 



fatigued by prolonged effort may lose its power of contraction to 

 such a degree that it becomes abnormally distended by the pres- 

 sure of the contained blood (cardiac dilatation, insufficiency of 

 the heart), with ensuing disturbance of the circulation. Over- 

 stinuilation of the nervous system by sudden psychical shock is 

 not only in man productive of serious results; fright palsy with 

 cessation of cardiac action (paraplexis) has also been observed 

 in the lower animals (fowls). 



A graduall}- and onl}- moderately increasing demand upon the 

 muscles and glands acts as a stimulus to their functional activity, 

 provided proper nutrition be afforded the tissue, and results in func- 

 tional hypertrophy, that is, in an increased grozvth of the cellular 

 elements corresponding to the demand' for zvork. This may be 

 noted especially in tubular structures provided with muscular 

 walls (smooth muscle), where there is gradually and spontane- 

 ouslv developed an increasing competence for the w^ork required 

 of the muscle, as in the thickening of the muscular layers of the 

 bladder in case of gradually narrowing stricture of the urethra 

 (v. functional hypertrophy). 



Thermic Influences. 



High temperature of the surrounding atmosphere (above the 

 body temperature peculiar to the animal) may lead to failure of 

 heat loss (heat stasis) and hyperthermia of the entire body with 

 fatal termination by so-called heat-stroke. This is frequently ob- 

 served in hogs when crowded in railway cars. The condition is 

 most easily induced if the dissipation of the body heat by evapora- 

 tion is diminished, and at the same time heat production in- 

 creased in the animal by prolonged muscular eft'ort or by rich 

 feeding. (It is known from experiments that warm-blooded ani- 

 mals kept in well-ventilated warm chambers at 36 to 40° C. 

 die, some in from one to three days, others in from ten to thirty 

 days. The body temperature of such animals — rabbits — rises to 

 39 to 42° C. ; they become dyspnoeic and there is increase in 

 the frequency of the -pulse; the haemoglobin of the blood is re- 

 duced, and degenerative changes develop in the heart, the liver 

 and kidneys. — Ziegler.) The cause of death is cardiac failure 

 (heat rigidity) occasioned by the overheated blood, or may de- 

 pend upon a thickening of the blood through excessive loss of 

 fluid by sweating and respiration (fall of blood pressure, dimi- 



